The present invention relates to a solar heat powered plant provided with a steam supply system, a hot-water supply system, and a hot-water tank for common use of both systems; and, more specifically, to an improvement of a solar heat powered plant in which water in a hot-water tank can be heated to a desired temperature in a short time and which can supply heat energy based on heat energy required.
FIG. 1 is a system diagram which schematically shows a heat-electric complex type solar heating system, as one example of a conventional solar heat powered plant. This solar heat powered plant is provided with a steam supply system A for feeding high-temperature steam to a high-temperature-side heat load unit, and a hot-water supply system B for feeding hot water to a low-temperature-side heat load unit.
As shown in FIG. 1, the prior art solar heat powered plant comprises: a hot-water tank 1 for storing hot water; a hot-water supply tank 2 for supplying hot-water; high and low-temperature-side heat load units 3A and 3B; a return tank 4 for temporarily storing low-temperature water from the low-temperature-side heat load unit 3B; and high and low-temperature-side heat exchangers 5A and 5B. The prior art solar heat powered plant further comprises high and low-temperature-side solar heat collectors 6A and 6B of a condenser type; pumps 7A, 7B, 8A, 8B, 9 and 10 attached to individual pipe lines; and a check valve 11 attached to a secondary-side inlet pipe 12 which extends from the return tank 4 to the low-temperature-side heat exchanger 5B.
In the hot-water supply system B, heat energy obtained through the solar heat collector 6B is supplied to the heat exchanger 5B, where hot water is produced from low-temperature water, via heat exchange. The hot water thus produced is stored in the hot-water tank 1. The hot water in the hot-water tank 1 is taken out as required and is fed into the hot-water supply tank 2, where it is further supplied to the low-temperature-side heat load unit 3B, such as a high-temperature-water supply unit or a heating system. Thereafter, the hot water is deprived of its heat energy by the load unit 3B, being reduced to low-temperature water, and is stored once in the return tank 4. Next, the low-temperature water is re-heated into hot water by the heat exchanger 5B, and the hot water thus re-heated is stored in the hot-water tank 1.
In the steam supply system A, the hot water from the hot-water tank 1 is further heated by the heat exchanger 5A, using heat energy obtained through the solar heat collector 6A. Thus, high-temperature steam is produced. The steam produced in this manner is supplied to the high-temperature-side heat load unit 3A such as steam power generation or industrial processing. Deprived of heat energy by the high-temperature-side load unit 3A, the high-temperature steam is converted into hot water, which is then returned to the hot-water tank 1.
Thus, according to the system in which high-temperature steam and hot water are fed to high and low-temperature-side heat load units 3A and 3B, respectively, using solar energy, the temperature of the hot water in the hot-water tank 1 must be fully raised to a desired temperature required to the high-temperature-side heat load unit 3A by the high-temperature side heat exchanger 5A, in order to produce high-temperature steam. This heating operation of the hot water is achieved by circulating water through the hot-water tank 1, the hot-water supply tank 2, the low-temperature-side heat load unit 3B, the return tank 4, the heat exchanger 5B; and, again, through the hot-water tank 1, in the order named, bringing the low-temperature-side heat load unit 3B to a no-load state.
Since the heating operation is usually performed during the morning hours, when solar radiation is faint, the amount of heat exchanged in the low-temperature-side heat exchanger 5B is not very great. Therefore, since the heating of the hot water in the hot-water tank 1 is time consuming, the start of the operation of the steam supply system A is liable to be delayed. Moreover, since the temperature within the hot-water tank 1 is lowered at night, after prolonged suspension of the operation, or after replacement of the circulating water, the heating operation tends to be time consuming for these reasons also.